Liver fatty acid binding protein is the mitosis-associated polypeptide target of a carcinogen in rat hepatocytes.

Abstract

Hepatocytes in normal rat liver were found previously to contain a cytoplasmic 14,000-dalton polypeptide (p14) that is associated with mitosis and is the principal early covalent target of activated metabolites of the carcinogen N-2-fluorenylacetamide (2-acetylaminofluorene). The level of immunohistochemically detected p14 was low when growth activity of hepatocytes was low, was markedly elevated during mitosis in normal and regenerating livers, but was very high throughout interphase during proliferation of hyperplastic and malignant hepatocytes induced in rat liver by a carcinogen (N-2-fluorenylacetamide or 3'-methyl-4-dimethylaminoazobenzene). We report here that p14 is the liver fatty acid binding protein. The nucleotide sequence of p14 cDNA clones, isolated by screening a rat liver cDNA library in bacteriophage lambda gt11 using p14 antiserum, was completely identical to part of the sequence reported for liver fatty acid binding protein. Furthermore, the two proteins shared the following properties: size of mRNA, amino acid composition, molecular size according to NaDodSO4 gel electrophoresis, and electrophoretic mobilities in a Triton X-100/acetic acid/urea gel. Their pI values overlapped in 2-dimensional isoelectric focusing/NaDodSO4 gel electrophoresis and showed the same response to delipidation. Either polypeptide reacted with and blocked the antiserum raised against the other polypeptide. The two polypeptides bound oleic acid similarly. Finally, identical elevations of cytoplasmic immunostain were detected specifically in mitotic hepatocytes with either antiserum. The collected findings are suggestive that liver fatty acid binding protein may carry ligands that promote hepatocyte division and may transport certain activated chemical carcinogens.

Mechanisms underlying generation of gradients in gene expression within the intestine: an analysis using transgenic mice containing fatty acid binding protein-human growth hormone fusion genes.

“…4B). These regional differences in murine L-FABP expression have been noted in the rat by some (Custer and Soroff 1984;Bassuk et al 1987), but not all, investigators (Capron et al 1979).…”

Antioxidative function of L-FABP in L-FABP stably transfected Chang liver cells

“…Methionine and cysteine amino acids are regarded as cellular scavengers of activated xenobiotics and involved in antioxidation. 8 However, the direct role of L-FABP in oxidative stress has not been investigated. In this report, we used an L-FABP stably transfected Chang liver cell line to test the hypothesis that hepatocyte L-FABP is an important cellular antioxidant during oxidative stress induced by hydrogen peroxide and hypoxia/ reoxygenation.…”

Preferential binding of growth inhibitory prostaglandins by the target protein of a carcinogen.

“…The preferential binding of the growth inhibitory cyclopentenone prostaglandins by L-FABP in vitro may be related to the specific covalent binding of the reactive metabolites of FAA carcinogen to that same protein during hepatocarcinogenesis in rats (5,6). The actions of L-FABP as the common and specific target of both types of ligands suggest the possibility that the reactive metabolites of the carcinogen may usurp the cellular machinery of the growth inhibitory prostaglandins in rat hepatocytes in a process important in carcinogenesis.…”

“…The liver carcinogen N-(2-fluorenyl)acetamide (2-acetylaminofluorene, FAA) is especially effective in bringing about such growth inhibition and is used for that purpose in the resistant cell model of Solt and Farber for the rapid induction of focal hyperplasia in rat liver (1). Liver fatty acid binding protein (L-FABP), generally considered to be an intracellular carrier offatty acids (2)(3)(4), is the principal early target protein of the reactive metabolites of FAA in rat liver (5,6). L-FABP is also a minor target of the liver carcinogenic aminoazo dyes (7).…”